Composition of lithium aluminoborosilicate glass and abrasive

The properties of glasses of the lithium-aluminoborosilicate system were investigated, namely, the density, spreadability, thermal expansion, and nature of crystallized phases at various temperatures. A crystal-optical analysis was conducted. The glasses were used to prepare abrasive compositions. Their strength properties were studied as a function of the composition of the glass binder and the regime of heat treatment.Translated from Steklo i Keramika, No. 3, pp. 27–30, March, 1996.     

Evaluation of boundary conditions for a mathematical model of heat transfer in a glass furnace

The results of a thermal engineering analysis of a bath furnace heated by natural gas with the surface area of the melting part equal to 303.3 m² and equipped with six pairs of burners are presented. Practical recommendations are given for increasing the efficiency of the furnace. The data can be used for developing a mathematical model of heat transfer in a glass furnace.Translated from Steklo i Keramika, No. 3, pp. 9–11, March, 1996.     

Calculi with the greatest number

Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 71–86, May–June, 1995.     

Fluidization of the active component of catalysts in catalytic formation of carbon assisted by iron and nickel carbides

A series of vanadium-tin mixed oxide catalysts have been prepared by the solid-state reaction of V₂O₅ and SnO₂ at 1250°C. The fresh and the used catalysts have been characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). High temperature oxygen chemisorption (HTOC) has been employed to titrate the coordinatively unsaturated vanadia sites. Ammoxidation of mesitylene has been carried out on these catalysts and an optimum composition of vanadium is arrived at. Better yields of tricyanobenzene (TCB) compared to literature values are obtained. A good correlation between the oxygen uptake and the TCB yield extends the applicability of HTOC to the fused oxide system.IICT Communication No. 3507.     

Solar collectors for the Beirut climate

The performance of solar collector systems is optimized for the Beirut climate with respect to the following parameters: angle of tilt and orientation, plate emissivity and number of glass covers. The Beirut hourly ambient temperature, wind speed, wind direction and the monthly averaged hourly and daily global, beam and diffuse radiation are used in the calculation of the useful harnessed energy, collector's efficiency, storage-tank temperature and other relevant parameters.

The optimal thermal performance of the solar collector in Beirut is obtained for a south-facing collector all the year with a slope angle equal to latitude +15° in winter and latitude −15° in the summer. The use of a selective surface of low emissivity in the collector gives a higher useful energy gain of about 25% in summer and 10% in winter as compared with a nonselective plate surface. The collector's daily efficiency, under optimal conditions, varies from 55 to 65% depending upon the month of the year.     

CO2 laser light scattering by bare soils for emissivitymeasurements: absolute calibration and correlation with backscatteringand composition

Measurements of the scattering cross section of a number of bare soils have been made with CO₂ laser illumination at 10.59 μm. The primary focus was on absolute calibration of the measurements. First, comparison of emissivity values resulting from the application of Kirchhoff's relation after angular integration of the bidirectional measurements, with emissivity values obtained from the analysis of the emitted radiation show excellent agreement to within less than 0.3%. Second, it was found that a simple formula holds for a relationship between the emissivity and co- and cross-polarized backscattering cross section at an angle of 30°. Third, a clear correlation was observed between emissivity and composition (in this case % Al+Fe oxides; % SiO₂) for a homogeneous series of samples from the same area in Niger. These results emphasize the importance of calibrated experimental data. The implications of the research give evidence of the advantage of obtaining emissivity from remote reflectivity measurements and possibly only backscattering measurements, and remotely estimating mineral composition     

Temperature and modulation characteristics of resonant-cavitylight-emitting diodes

Resonant-cavity light-emitting diodes (RCLED) are novel, high-efficiency light-emitting diodes which employ optical microcavities. These diodes have higher intensities and higher spectral purity as compared to conventional LEDs. Analytical formulas are derived for the enhancement of the spontaneous emission along the optical axis of the cavity. The design rules for high-efficiency operation of RCLEDs are established. The temperature dependence of the emission intensity is analyzed in the range 20-80° and it is described by an exponential dependence with a characteristic temperature of 112 K. The modulation characteristics of RCLEDs exhibit 3 dB frequencies of 580 MHz. Eye diagrams at transmission rates of 622 Mb/s are wide open indicating the suitability of RCLEDs for high-speed data transmission     

Laser ablation of diamond fibres and a diamond fibre metal matrix composite

Continuous chemical vapour-deposited diamond-coated fibres with tungsten wire or SiC fibre cores are attractive for reinforcing metals and ceramics. The fibres have been embedded in Ti-6A1-4V alloy to produce a diamond fibre-reinforced composite. Both the fibres and the composite material are extremely difficult to cut without damage by conventional mechanical methods. The use of a Nd-YAG laser to cut these materials is described.     

Composite ZrO2 fibre-based materials with double ammonium-cobalt and ammonium-magnesium diphosphates

The mechanism of solid-state interface interaction in systems of pure and stabilized zirconia fibres with ammonium-magnesium and ammonium-cobalt diphosphates has been studied. The investigation conducted makes it possible to control the preparation process of the composites. The optimal composition of dry slip was found to be 70 wt% of fibre and 30 wt% binder. The properties of the developed composite materials are presented.     

A.c. conductivity studies on the silver molybdo-arsenate glassy system

A new quaternary fast-ion conducting silver molybdo-arsenate [Agl-Ag₂O-(MoO₃ + As₂O₅)] (SMA) glassy system has been prepared using the melt-quenching technique for various dopant salt (Agl) concentrations by fixing the formers (MoO₃ + As₂O₅) composition and the modifier (Ag₂O) to formers (M/F) ratio. The prepared compounds were characterized by X-ray diffraction. The impedance measurements were made on different Agl compositions of the SMA glasses as a function of frequency (6.5 Hz–65 kHz) and temperature (303–343 K), using the Solatron frequency-response analyser (model 1250). The bulk conductivity and the appropriate physical model (equivalent circuit) of the SMA glass were obtained from the impedance analysis. The a.c. conductivity was calculated for different Agl compositions of SMA glasses at various temperatures and the obtained a.c. conductivity results were analysed using Jonscher's Universal Law. The conduction mechanism for the highest conducting SMA glassy compound has been explained using the diffusion path model.